[2.0.0-beta4] getEntityFieldStorageMetadata(): $entity_field_map must be of type array, null given

Closes #3477296

src/Plugin/Derivative/EntityFieldSourceDeriverBase.php

@@ -316,6 +316,9 @@ abstract class EntityFieldSourceDeriverBase extends DeriverBase implements Conta
         continue;
       }
       $entity_field_map = $all_entity_field_map[$entity_type_id];
+      if (!is_array($entity_field_map)) {
+        continue;
+      }
       $entityFieldsClassification = $this->getEntityFieldsClassification($entity_type_definition);
       $field_storage_definitions = $this->entityFieldManager->getFieldStorageDefinitions($entity_type_id);
       $fields_metadata[$entity_type_id]["field_storages"] = $this->getEntityFieldStorageMetadata($field_storage_definitions, $entity_field_map, $entityFieldsClassification);